Takaoka Yuichiro, Takahashi Moeka, Kurauchi Yuki, Hisatsune Akinori, Seki Takahiro, Shudo Koichi, Katsuki Hiroshi
Department of Chemico-Pharmacological Sciences, Graduate School of Pharmaceutical Sciences, Kumamoto University, Kumamoto, Japan.
Priority Organization for Innovation and Excellence, Kumamoto University, Kumamoto, Japan; Program for Leading Graduate Schools "HIGO (Health life science: Interdisciplinary and Glocal Oriented) Program", Kumamoto University, Kumamoto, Japan.
Int Immunopharmacol. 2016 Sep;38:367-76. doi: 10.1016/j.intimp.2016.06.025. Epub 2016 Jun 25.
Accumulating lines of evidence suggest that retinoic acid receptor agonists such as Am80 exerts anti-inflammatory actions in the central nervous system, although detailed mechanisms of the action remain largely unknown. Our previous findings suggest that Am80 provides therapeutic effect on intracerebral hemorrhage in mice via suppression of expression of chemokine (C-X-C motif) ligand 2 (CXCL2). Here we investigated the mechanisms of inhibitory action of Am80 on expression of CXCL2 and other pro-inflammatory factors in microglial BV-2 cells. Pretreatment with Am80 markedly suppressed lipopolysaccharide (LPS)-induced expression of CXCL2 mRNA and release of CXCL2 protein. Am80 had no effect on LPS-induced activation of p38 mitogen-activated protein kinase and extracellular signal-regulated kinase. On the other hand, Am80 prevented LPS-induced nuclear translocation of p65 subunit of NF-κB complex. In addition, total expression levels of p65 and IκBα proteins, as well as of mRNAs encoding p65 and IκBα, were lowered by Am80. Dependence of CXCL2 expression on NF-κB was confirmed by the effect of an NF-κB inhibitor caffeic acid phenethyl ester that abolished LPS-induced CXCL2 expression. Caffeic acid phenethyl ester also abolished LPS-induced expression of inducible nitric oxide synthase, interleukin-1β and tumor necrosis factor α, which may be relevant to the inhibitory effect of Am80 on expression of these pro-inflammatory factors. We additionally found that Am80 attenuated LPS-induced up-regulation of CD14, a co-receptor for Toll-like receptor 4 (TLR4). These results suggest that inhibitory effect on TLR4 signaling mediated by NF-κB pathway underlies the anti-inflammatory action of retinoic acid receptor agonists in microglia.
越来越多的证据表明，诸如Am80之类的视黄酸受体激动剂在中枢神经系统中发挥抗炎作用，尽管其详细作用机制在很大程度上仍不清楚。我们之前的研究结果表明，Am80通过抑制趋化因子（C-X-C基序）配体2（CXCL2）的表达，对小鼠脑出血具有治疗作用。在此，我们研究了Am80对小胶质细胞BV-2中CXCL2及其他促炎因子表达的抑制作用机制。用Am80预处理可显著抑制脂多糖（LPS）诱导的CXCL2 mRNA表达及CXCL2蛋白释放。Am80对LPS诱导的p38丝裂原活化蛋白激酶和细胞外信号调节激酶的激活没有影响。另一方面，Am80可阻止LPS诱导的NF-κB复合物p65亚基的核转位。此外，Am80降低了p65和IκBα蛋白的总表达水平以及编码p65和IκBα的mRNA水平。NF-κB抑制剂咖啡酸苯乙酯可消除LPS诱导的CXCL2表达，从而证实了CXCL2表达对NF-κB的依赖性。咖啡酸苯乙酯还消除了LPS诱导的诱导型一氧化氮合酶、白细胞介素-1β和肿瘤坏死因子α的表达，这可能与Am80对这些促炎因子表达的抑制作用有关。我们还发现，Am80可减弱LPS诱导的Toll样受体4（TLR4）共受体CD14的上调。这些结果表明，对视黄酸受体激动剂在小胶质细胞中的抗炎作用而言，对由NF-κB途径介导的TLR4信号传导的抑制作用是其基础。
